1. Field of the Invention
This invention relates to the processing of organic waste materials for the recovery of useful products therefrom by non-oxidative thermal decomposition.
High molecular weight organic wastes from both industry and the consumer have long presented a disposal problem. Some materials, such as hard nut shells and certain fruit seeds, by-products of the agricultural industry, have a high oil content which discourages the industry from using common means of disposal. Other materials, such as used rubber tires, liberate large amounts of soot and other atmospheric pollutants when burned. A further problem is the high energy consumption inherent in many disposal processes and the loss of useful organic values.
A need therefore exists for an energy efficient and environmentally sound process and apparatus for recovering organic values in a useful form from organic waste materials.
2. Description of the Prior Art
Reaction vessels and processes for the carbonization or destructive distillation of organic material are widely disclosed. Examples of disclosures most pertinent to the present invention are the rotating vessels of Frank, U.S. Pat. No. 1,677,757, issued July 17, 1928; Goodell, U.S. Pat. No. 2,265,158, issued Dec. 9., 1941; and Taciuk, U.S. Pat. No. 4,285,773.
The present invention is of particular interest in the processing of scrap rubber, typically in the form of used automobile tires. A variety of methods for processing scrap rubber are known.
One such method is the "digester" process, in which ground scrap rubber is heated under pressure in a solution of a cellulose-destroying chemical such as caustic soda, calcium chloride and zinc chloride. This treatment destroys the fiber present in the rubber and plasticizes the rubber. Swelling oils are usually added to enhance the process. Such processes are described in Carr, et al., U.S. Pat. No. 2,567,802, issued Sept. 11, 1951; Elgin, U.S. Pat. No. 2,593,279, issued Apr. 15, 1952; Brown, et al., U.S. Pat. No. 2,640,035, issued May 26, 1953; Green, U.S. Pat. No. 2,879,245, issued Mar. 24, 1959; and Soott, U.S. Pat. No. 3,700,615, issued Oct. 24, 1972.
In another method, known as the "heater" process, ground scrap rubber is heated with live steam under pressure, usually with the addition of softening agents, until the rubber becomes plasticized. Descriptions of such processes are found in Mankowich, et al., U.S. Pat. No. 2,871,206, issued Jan. 27, 1959, and Glenn, et al., U.S. Pat. No. 3,272,761, issued Sept. 13, 1966.
Mechanical processes, which involve mechanical working of the rubber at elevated temperature, are described in Sverdrup, U.S. Pat. No. 2,809,944, issued Oct. 15, 1977; Sverdrup, U.S. Pat. No. 2,845,395, issued July 29, 1958; Dasher, U.S. Pat. No. 2,853,742, issued Sept. 30, 1958; Dasher, U.S. Pat. No. 2,966,468, issued Dec. 27, 1960; Lee, et al., U.S. Pat. No. 4,049,588, issued Sept. 20, 1977; and Maxell, U.S. Pat. No. 4,146,508, issued Mar. 27, 1979.
Dissolving processes, using a hydrocarbon solvent at elevated temperatures, are also known. An example is that described by Wakefield, et al., in U.S. Pat. No. 3,896,059, issued July 22, 1975.